Bromoacetate lysine residues

Haloacetates. In alkaline solution lysine residues can be alkylated in the presence of iodo- or bromoacetate ions (118). Both mono- and di-carboxymethyl derivatives can be formed. Some of the characterized derivatives are listed at the end of Table VI. Number 25, t-CM-Lys-41-RNase, shows a very low activity when measured by a step 2 assay employing C > p as substrate. This same compound is active in the depolymerization of 5S RNA (119) but the evidence presented to show that it is not the result of contamination with native RNase-A can be interpreted to suggest the opposite. 

The hydrophobic portion of the reagent, but not adenine, appears to be essential for the alkylation of the adenosine deaminase active site since benzylbromoacetate irreversibly inactivates the enzyme whereas the site is inaccessible to haloacetate and its amide. Benzylbromoacetate and 9-(p-bromoacetamidobenzyl) adenine are only 4 and 2.5 more reactive, respectively, than bromoacetate toward 4-(p-nitrobenzyl)pyridine. The oxidation of ribose of purine riboside with periodic acid in order to produce carbonyl groups that may react with lysine residue destroys the inhibitory effectiveness of the nucleoside. ... 

Reactions of C enriched reactants with biologically interesting molecules have also been monitored by C NMR. Nigen et al. (184) carboxymethylat-ed harbor seal and sperm whale cyanoferrimyoglobin with enriched [2-i C] bromoacetate. Adducts of the NHg terminal residues of histidine and lysine were observed in the > C spectra. In denatured cyanoferrimyoglobins all histidine residues were converted to the dicarboxymethyl derivative. 

---